The present invention relates to a pneumatic tire, more particularly to a tread structure comprising siped tread elements capable of improving on-the-ice tire performance and uneven tread wear resistance.
In general, winter tires such as snow tire and studless tire are provided in the tread portion with a tread pattern comprising a number of siped blocks, and the sipes are oriented axially of the tire for the purpose of deriving a maximum driving force (traction) and a maximum braking force from their edges (so called edge effect).
In such a block pattern tire, however, during running on icy roads, cornering power becomes insufficient in comparison with the driving force. Therefore, the steering stability is not so good during straight running as well as cornering. Thus, on the whole, there is room for improvement in ice performance. Further, as the block which is provided with axially oriented sipes (a) as shown in FIG. 7 is greatly decreased in circumferential rigidity, so called heel-and-toe wear—uneven wear between the circumferentially opposite edges of the block—is caused. This is especially remarkable in winter tires wherein a relatively soft rubber compound is used in the tread portion.